Solenoid

ABSTRACT

A solenoid ( 1 ) comprising at least two stationary coils ( 2, 3 ), which are located axially beside each other and are current supplied at the same time, and at least one magnetically active element ( 4, 5 ), such as a permanent magnet or a soft iron part. The solenoid contains one inner and one outer magnetically active element ( 4, 5 ), of which at least one is composed of an essentially axially magnetized permanent magnet ( 4, 5 ). The coils are located between the elements ( 4, 5 ), so that they surround the inner element ( 4 ), and are arranged with mutually different current direction, and the coils and the elements ( 4, 5 ) are arranged around an essentially mutual axis center line ( 6 ), so that a magnetic field is obtained between the elements ( 4, 5 ) and this crosses the current supplied coils&#39; ( 2, 3 ) wire essentially perpendicularly and gives rise to an axial power action between the coils and the elements, and at least one of the elements is axially movable.

BACKGROUND OF THE INVENTION

The subject invention refers to a solenoid, comprising at least twostationary coils, which are located axially beside each other and arecurrent supplied at the same time, and at least one magnetically activeelement, such as a permanent magnet or a soft iron part.

Solenoid devices have many different fields of application. They can forinstance switch over circuit-breakers or valves. One example of anutmost demanding application is to be used as a fuel valve in afuel-supply system for an internal combustion engine. The presentinvention is based on such an application. The valve shall be able toopen and close with a frequency of up to 300 Hz, at the same time as itsconsumption of energy must be low. In the current absence state thevalve shall be open, i.e. it shall have one opening position only.Obviously it should also have a simple, cheap, dependable construction.

It is very difficult for a conventional solenoid with a winding andparts of soft iron to fulfill, the outlined claims. It has greatinertia, both electrically, by high inductance, and mechanically.Further it has many parts and is relatively complicated GB 1228539 andGB 2228831 show solenoids having two coils located axially beside eachother. But these coils are used alternately and therefore no higherpower than for the conventional solenoid can be achieved. It is alsoknown to use a movable permanent magnet, which is driven by means of twosurrounding and at the same time current supplied coils. The coils aresurrounded longitudinally and radially outwards by soft iron parts,which direct the magnetic flow. The coils have opposite currentdirection, so that they form a mutual pole in the soft iron part, whichseparates them. These solenoids have a relatively complicatedconstruction since they have soft iron lids in both ends and a soft ironring in the middle in order to direct the magnetic flow.

GB 1136418, DE 3426688, JP 57-198.611 show examples of this type ofsolenoids, which have two holding positions when they are not suppliedwith power. U.S. Pat. No. 4,422,060 shows a solenoid with a holdingposition. All those have a light-weight permanent magnet, but acomplicated magnetic frame, which closes the magnetic flow.

DE 4040120 shows a permanent magnet surrounded by one or two coils.These coils are not at all surrounded by any soft iron parts. Thedescription is very brief, e.& nothing is mentioned about currentdirection in the coils or how the permanent magnet's poles are placed.The coils are placed in a relatively large distance from each other. Thetuning of the length of the permanent magnet and the coils' mutualdistance is such that one of the ends of the permanent magnet is locatedin an “explosive point” and the other one in an “implosive point”. Thedescription is brief and “phenomen-accentuated”. It seems that the coilshave the same current direction and such a large mutual distance, sothat their power action on the permanant magnet can be able tocooperate.

SUMMARY OF THE INVENTION

The purpose of the subject invention is to essentially reduce the aboveoutlined problems.

The above mentioned purpose is achieved in a solenoid, according to theinvention, having one inner and one outer magnetically active element,of which at least one is composed of an essentially axially magnetizedpermanent magnet, and the coils are located between the elements, sothat they surround the inner element, and are arranged with mutuallydifferent current direction, and the coils and the elements are arrangedaround an essentially mutual axial centre line, so that a magnetic fieldis obtained between the elements and this crosses the current suppliedcoils' wire essentially perpendicularly and gives rise to an axial poweraction between the coils and the elements and at least one of theelements is axially movable. Consequently, the two coils are notsurrounded in anal direction by any soft iron parts, which direct themagnetic flow between one inner and one outer magnetically activeelement. The flow crosses instead the current supplied coils' wireessentially perpendicularly. Accordingly, by means of this the way offunction differs from the majority of known solutions. The magneticfield flows between one outer and one inner magnetically active element,which definitely separates the present invention from DE 4040120, justlike the mutually different current direction of the coils. Thisconstruction leads to a simple design with very good performance. As themagnetic flow is passing essentially radially between one inner and oneouter magnetic element a very good power action is created betweenmagnetic elements and winding As the coils have mutually differentcurrent direction the inductance of the solenoid becomes extremely low.This contributes to high rapidity and low consumption. These and othercharacteristic features and advantages will become more apparent fromthe detailed description of various embodiments with the support of theappended drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in closer detail by means of variousembodiments with reference to the accompanying drawing.

FIG. 1 is a cross-sectional view of a solenoid in accordance with theinvention. Its permanent magnet is located in the middle of the solenoidand axially movable, in this case vertically.

FIG. 2 shows a cross-section of a cut along line II—II in FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the schematical FIG. 1 numeral reference 1 designates a solenoid Itsparts are essentially concentrically arranged around an axial centreline 6. Two coils 2, 3 are located axially beside each other and arearranged around the centre line 6. They are wound in separate recessesin a coil former 14. The coils are arranged with mutually differentcurrent direction. The easiest way to achieve this is to have differentwinding direction for the coils 2, 3 respectively. The winding wire isthen running over the intermediate portion 15, which delimits the bothcoils. But of course, respective coil can also be individuallyelectrically connected, provided that mutually different currentdirection is attained. In the middle of the coil former 14 there is arecess, where one 4 is so arranged that it is axially easy movable. Inthe shown embodiment the inner element 4 is an essentially axiallymagnetized permanent magnet, but it could also be composed of a softiron part or similar. An axially magnetized permanent magnet has theadvantage of being very light-weight. Considering that high rapidity isnecessary this is of course an advantage. By axially magnetized is meantthat it is so magnetized that at its one end, seen from an axialdirection, there is a north pole, while at its other end, there is asouth pole. The coil former 14 is made of a non-magnetic material,usually a plastic material and is arranged with guides for the innerelement 4. The coil former 14 with the two coils 2 and 3 is surroundedby an outer magnetically activated element 5. In this case it is a softiron sleeve or similar. Outer and inner elements 5, 4 as also the coils2, 2 are usually circular, and coaxially arranged around a center line6. But obviously they could also have another shape.

In the shown embodiment only the inner element 4 is axially movable.Generally this is preferable, but other embodiments can also beconceivable. The outer element 5 can be anally movable alone, or, boththe outer and inner element can be axially movable. In the latter caseboth elements 4, 5 are preferably combined at one of their ends, in thiscase the upper end. Another example of embodiment is that the outerelement 5 is composed of an axially magnetized permanent magnet, whilethe inner one is composed of a soft iron body or similar. Further bothelements 4, 5 can be composed of anally magnetized permanent magnetswith mutually reversed magnetization direction In the above examples theouter or the inner element or both elements can be axially movable. Inthose cases when the elements 4, 5 are composed of a soft iron part anda permanent magnet, the lengths are preferably chosen according to thefollowing That of the elements 4, 5, which is composed of a soft ironpart or similar, shall at least have as large axial length as the totalaxial length of the coils 2, 3. This length is in its turn at least aslarge as the length of the element, 4, 5, which is composed of apermanent magnet. Normally these differences in length are small.

FIG. 1 shows an embodiment where the solenoid is adapted to function asa stop valve for a fuel flow. The coils 2, 3 and the elements 4, 5 areenclosed by a housing 7, 13. The housing 7 has a cylindrical opening inwhich the elements 4, 5 and the coil former 14, together with the coils2, 3, are inserted In this case the coil former 14 has an end wall. 13,which completely seals the opening in the housing 7. Obviously alsoother kind of enclosures could be conceivable. A washer 16 is locatedbetween the-end of the outer element 5 and a projecting flange at thecoil former 14. Obviously this washer could be excluded. A speciallocking washer 7 is holding the coil former 14 in an axial directionrelative to the housing 7. A number of inlet openings 8 and outletopenings 9 are formed in the housing 7 and located in such a manner thatat least either the inlet openings or the outlet openings are sealed bythe inner. element 4 or. the outer element 5, when this is to be foundin an end position. In the shown example the outlet opening 9 is sealedby the inner element 4 when this has been moved to its opposite endposition. The outlet opening 9 is thus located in the end wall 10 of thehousing and is sealed by the inner element 4, when this is to be foundin its end position towards the end wall 10. Obviously, on the otherhand the inlet opening 8 could have this location. A sealing 11 islocated on the inner element 4 in order to seal between the element andthe end wall. Obviously the sealing 11 could also be located on the endwall and have an aperture for the opening 9. In FIG. 2 is shown that anumber of recesses 18 are formed in the internal surface of the coilformer 14 turned against the inner element 4. These recesses makes afuel circulation possible around the inner element 4 when this is movingA recess 19 in the internal edge of end wall 13 of the coil former 14associates to the recesses 18. By means of these recesses 18, 19 theinner element will not be slowed down when moving. Obviously therecesses 18, 19 can be made larger than those shown. A pin may be usedfor electrical connection of the two coils 2, 3.

In the shown position of the inner element 4 fuel can flow between inletopening 8 and outlet opening 9. The inner element 4 is kept in thisposition by means of a soft iron part 12, or similar, being located inthe end wall 13. The element is thus kept in this position without anyneed of current to the coils. In the present application this means bothan energy-saving and an increased reliability compared with the casethat a special holding current should be added to the coils 2, 3, inorder to keep the inner element 4 in its lower position, which allowsthe fuel to pass through the openings 8 and 9. For blocking thethoroughfare of fuel a very strong location altering current issupplied, making the element 4 go fast up to the end wall 10. Thereaftera weaker holding upwards current is supplied in order to maintain asealing against the end wall 10. This holding current is approximatelyonly a fifth of the size of the location altering current. In order toopen the fuel supply rapidly a strong location altering current issupplied in the opposite direction to the earlier one, i.e. for amovement downwards. No holding current is needed since the soft ironpart 12 is located in the end wall 13 opposite the end wall 10 with theopenings 8, 9. In a further application a soft iron part 12 could belocated in the end wall 10 in order to provide a valve normally closed.Obviously also soft iron parts could be used in both end walls 10, 13.

What is claimed is:
 1. A solenoid (1) comprising: a coil assemblyconsisting of two stationary coils (2, 3), which are located axiallybeside each other and are current supplied at the same time, andmagnetically-active inner and outer elements of which at least one iscomposed of a single essentially axially magnetized permanent magnet (4,5), wherein the coils are located between the inner and outer elements(4, 5), so that they surround the inner element (4), and are arrangedwith mutually different current directions, and the coils and the innerand outer elements (4, 5) are arranged around an essentially mutualaxial center line (6), so that a magnetic field is obtained between theinner and outer elements (4, 5), said magnetic field crosses the currentsupplied coils essentially perpendicularly to wires defining the coilsand gives rise to an axial power action between the coils and the innerand outer elements, wherein at least one of the inner and outer elementsis axially movable.
 2. A solenoid (1) according to claim 1 wherein onlythe inner element is axially movable.
 3. A solenoid according to claim1, wherein the outer element is composed of the axially magnetizedpermanent magnet, while the inner element is composed of a soft ironsleeve.
 4. A solenoid (1) according to claim 1 wherein the inner elementis composed of the axially magnetized permanent magnet and the outerelement is composed of another axially magnetized permanent magnet.
 5. Asolenoid according to claim 1, wherein the inner element is composed ofthe axially magnetized permanent magnet, while the outer element iscomposed of a soft iron sleeve.
 6. A solinoid (1) according to claim 5wherein the outer element has an axial length at least as large as thetotal length of the coils. which in turn, is at least as large as thelength of the inner element.
 7. A solinoid (1) according to claim 1further comprising: a housing at least partially enclosing the coils andthe inner and outer elements. said housing having an inlet opening andan outlet opening formed therein. said inlet and outlet openings beinglocated such that at least one of the inlet and outlet openings isclosed by said axially-movable one of the inner and outer elements whensaid axially-movable one of the inner and outer elements is in an endposition.
 8. A solinoid (1) according to claim
 7. wherein the housingcomprises an end wall through which said one of the inlet and outletopenings extends.
 9. A solenoid (1) according to claim 8, wherein saidaxially-movable one of the inner and outer elements is the innerelement. and wherein the solenoid further comprises a sealing (11)disposed on at least one of the inner element (4) and the end wall (10),in order to seal between the inner element and the end wall.